Traffic signal system



July 4, 1933. M. B. THOMPSON 1,917,165

TRAFFIC SIGNAL SYSTEM Filed May 8, 1930 G OneWa Y Srreei' I I Mi.

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ATTORNEY Patented July 4,, 193

STATES JUN B. THOMPSON, CF LOUISVILLE, KENTUCKY TRAFFIC SIGNAL SYSTApplication filed May 8 1930. Serial No. 450,607.

This invention relates to trafic signal systems for regulating vehiculartrafic at street intersections. At the present time street intersectiontraffic signal regulations vary quite widely in the difierentcommunities and quite often the regulations in the congested areas ofany particular community differ from those employed in the other areasofthe same community. Particularly isthis true in conim nection with thepermissible turns at the The regulations various street intersections.in this respect difier more widely'than in any other phase of traficcontrol with the result that a person traveling from one community toanother is often at a loss to know how to proceed.

The three light, three color-green, yellow and redtraiiic signal hasbeen adopted by practically all communities using signal lights and hascome to be considered as the standard signal. With this type, thegenerally accepted or standard regulations are that the green or golight is a signal permitting movement in any direction except asmodified by the turn regulations, the red or stop light is a signalprohibiting movement in any direction except as modified by the turnregulations while the yellow or caution light is a si 'al of theapproaching change of lights. 11 some communities additional lights areemployed to inform the traveler as to the permissible or non-permissibleturns as the case may be. Naturally additional lights require additionalcontrol apparatus, larger signal supports and are otherwise considerablymore expensive than the standard three light signal alone. A "lessexpensive arrangement utilized by other communities to inform travelersof permissible turns consists" in the use of printed signs in connectionwith the standard three light signal. The use of printed signs, however,is ob jectionable inasmuch as they must be laced out of the line ofvision from the tra c flow to the signals where they are very apt to beoverlooked. Consequently they are not highly eflicient in the preventionof accidents or traflic regulation violations. They are alsoobjectionable because of their unsightliness which is accentuated by theconspicuous position in which they must be placed to accomplish theirpurpose even inefficiently. Furthermore such signs must be printed inbig bold type in order to be readable thereby necessitatingcomparatively large signs atcorners having more than one turn regulationsuch, for example, as corners where left turns are not permitted on thego signal and right turns are permitted on the stop signal. Ubviously anincrease in the size of the signs further accentuates theirunsightliness and, at the same time, requires heavier and more expensivesupports than otherwise in order to meet the increase in Weight and Windresistance.

The principal object of the present invention is to provide a traflicsignal system, uti-- lizing the standard three light signal, which willfully inform travelers of the permissible or non-permissible turns ateach specially regulated intersection, and, which will accomplish thisobject without the use of print-.' ed signs, additional lights or othersimilarly objectionable or expensive equipment.

A further object is to provide a traflic signal system of the characterstated in which the standard three light signal units of existingsystems may be utilized without requiring any change in the position,location, or operation of the various units comprising the system andwithout entailing any material expenditure of time or money.

Generally stated, the invention consists in arranging in the line ofvision from the traflic flow to the non-standard turn-regulated stopand/or gosignals of a standard three light signal, a directionindicating symbol to indicate positively the permissible turn andthereby negatively show the non-permissible turn. By placing thedirection indicating symbol in the line of vision as stated, a travelerapproaching a non-standard turn-regulated intersection and looking atthe turn-regulated signal must, of necessity, see the indicator.Consequently he is instantly informed of the 95 turn regulation and thusnot required to hesitate and search for printed signs or other sourcesof information. It should be understood that the. direction indicatingsymbols need only be used in connection with signal 1 units located atstreet intersections having one or more non-standard turn regulations.Naturally at the intersections having the generally accepted or standardregulations, the traveler knows instantly, upon seeing the green signal,that he is permitted to make either turn, and, upon seeing the redsignal,

manner in the line of vision between the flow Jae of traffic and theparticular signal to which it may apply. Preferably the indicator ismade of triangular form as shown at 1 in Figure 1 and is applieddirectly to the lens 2 of the signal light as by painting it thereon orpasting a suitable triangular form thereto. The lens 2 is positioned atthe proper signal light of its particular signal unit in a manner suchthat the apex 3 of the symbol points in the direction of the permissibleturn.

The. diagrammatic layout shown in Figure 2 illustrates the applicationof the invention to a standard three light traffic signal system. Inthis case a series of vehicles 4, '5, 6, and 7 are shown as travelingalong the same street in the direction of the arrow A, each vehiclebeing about to cross a different intersection. Each of the intersectionsis controlled by a different three light signal unit, the go or green,caution or yellow, and stop or red,

signals of each unit being indicated respectively by the letters G, Yand lit.

The first intersection that is to say the one which vehicle 4' is aboutto cross, is shown as a standardly regulated intersection. The driver ofthis vehicle, upon looking at the signals, will immediately know: if thesignal be green, that he may go straight ahead or make either turn; and,if it be red, that he is not permitted to move in any direction.

The driver of the next vehicle (5) by looking at the signal, will seethe direction indicator 1 on green only, and, since it points to theleft, he will immediately know: if the signal be green, that he may gostraight ahead or turn to the left only; and, if it be red, that he isnot permitted to move in any direction. Thus this driver, simply bylooking at the signal, a required act in any signal system, is instantlyand fully informed of the non-standard regulations controlling the flowof traffic at this intersection. The signal thus operates to prevent thedriver from making a wrong turn whether or not he is aware of the factthat the cross street is a one way street permitting travel to the leftonly. Furthermore it will tend to make him aware of the fact that thecross street is a one way street without requiring the use of signs topoint out such fact.

At the next intersection, the cross street is shown as another one waystreet permitting travel to the right only. In this case the driver ofthe vehicle 6 by looking at the signal, will see direction indicators 1pointing to the right on both red and green, and consequently he willimmediately know: ifthe signal be green, that he may go straight aheador make a right turn only; and, if the signal be red, that he ispermitted to make a right turn. The advantages of the indicator withrespect to the one way phase of the intersection, are again apparent.

By looking at the signal of the last intersection, the driver of thevehicle 7 will see a direction indicator 1 pointing to the right on redonly, and consequently he will immediatelyknow: if the signal be green,that he may go straight ahead or make either turn; and, if the signal bered, that he is permitted to make a right turn.

The foregoin is, of course, merely illustrative of the apphcation of theinvention and is made to bring out the advantages of the inventi on andis not to be construed as a limitation thereon. It is apparent from thisillustration that the invention may be easily, quickly and inexpensivelyapplied to existing systems utilizing standard three light signal unitsand that it eliminates the use of both unsightly signs and expensiveadditional light equipment. It has further advantages in that it iseasily understood and does not obscure the signal lights althoughpositioned directly in the line of vision.

Having described my invention, I claim:

1. In combination, a traffic light signal unit of the standard typehaving diiferently colored signals for the standard regulation oftraffic, and means permanently associated with one of said signalsmodifying the light emission therefrom for indicating the only turnpermissible on that signal.

2. In combination, a traffic light unit of the standard type havingdifferent colored signals for the routine regulation of traffic, andmeans permanently associated with one of said signals modifying thelight emission therefrom for indicating a special turnregulationapplying to that signal.

In testimony whereof I hereunto affix my signature this 6th day of May,1930.

MARION l3. THOMPSON.

